1. Field of the Invention
The present invention relates to a self-tapping tee with a coupling tap having a removable mandrel for use on heavy walled plastic pipe, such as polyvinyl chloride (PVC) pipe or thick walled polyethylene tubing, said self-tapping tee being useful without the mandrel on light walled plastic pipe or tubing.
2. Brief Description of the Prior Art
Plastic pipe is in common use in underground irrigation systems. Both light walled plastic pipe, such as polyethylene, and heavy walled plastic pipe, such as PVC and thick walled polyethylene tubing, are used. Heavy walled polyethylene tubing and PVC pipe have also been approved by various governmental agencies for natural gas.
With the advent of plastic pipe, it has been found that tapping tools for metal pipe are generally considered much too expensive for use with plastic pipe. Such tools for metal pipe are generally manufactured from high priced steel which is carefully machined and heat treated. In keeping with the change to plastic pipe, various tool designs of less expensive construction have been proposed.
There are self-tapping tees, formed of plastic material, for light walled plastic pipe such as described in U.S. Pat. No. 5,694,972 to King for Saddle Tee for Irrigation Lines. In this patent, a coupling tap is poked through polyethylene tubing or the like, with the sidewall of the tubing around the hole stretched about the tap, forming a seal.
Conventionally, when a plastic tee joint is installed on heavy walled plastic pipe, such as PVC or thick walled polyethylene, a hole is drilled or cut in the sidewall of the line. With a typical saddle tee for PVC pipe, glue is applied to the line, the saddle tee is snapped on the pipe over the glue and a hole is drilled in the line through a fitting after the glue has set. This operation is accompanied by some risk that the coupon or filings cut from the sidewall may be washed through the line and plug a valve or sprinkler head downstream from the tap. In use with PVC pipe, the King patent mentioned above teaches drilling a hole in the sidewall either before or after the tee is installed. Like other tee joints, the patent suggests gluing the self-tapping tee to the line and/or the use of O-rings or the like to ensure a good seal.